Armour

ABSTRACT

Armour ( 10 ) for dissipating energy associated with an impacting projectile, the armour ( 10 ) including an impact absorption layer ( 12 ) supported by a backing ( 14 ), the impact absorption layer including a plurality of macroscopic particles ( 16 ) and a plurality of microscopic particles ( 20 ) which are substantially encapsulated by an at least partially flexible matrix ( 18 ), the microscopic particles ( 20 ) and macroscopic particles ( 16 ) being arranged to interact with one another such that when at least one of the macroscopic particles ( 16 ) is moved during an impact, the movement is at least partially transferred to the microscopic particles ( 20 ) thereby assisting to dissipate the impact energy.

RELATED APPLICATIONS

This application claims priority from Australian provisional patentapplication no. 2013901435 filed on 24 Apr. 2013, the contents of whichare incorporated by reference.

TECHNICAL FIELD

The invention relates to armour. More specifically, the inventionrelates to an armour material, composite armour systems, armour platesand structures including such armour.

BACKGROUND

Armour is commonly used in military and civil applications to protect anunderlying object such as a structure or person from an incomingprojectile. Armour may be in the form of armour plates which are locatedon or incorporated within the structure such as a vehicle or locatedwithin clothing worn by the person.

Various configurations of armour plates have been proposed forredirecting an incoming projectile and absorbing the energy associatedwith the projectile. One such configuration is a composite armour platewhich includes a composite matrix material supported by a backing plate.The composite matrix material includes a layer or multiple layers ofhard ceramic spheres set in a polyurethane foam material.

When impacted by a projectile the hard ceramic spheres deflect theprojectile and also undergo limited movement within the polyurethanefoam material. This movement results in some of the kinetic energy ofthe projectile being transferred to the composite matrix. Accordingly,the energy of the projectile is at least partially dissipated within thecomposite matrix which assists to protect the underlying object from theprojectile.

A disadvantage of the above described armour plate configuration is thatduring the impact of the projectile there is limited interaction betweenthe hard ceramic spheres, the polyurethane foam material and the backingplate. As such, the effectiveness of the armour plate configuration todissipate, absorb and redirect energy of the projectile is limited.

The below described invention seeks to improve or overcome one or moreof the above identified disadvantages and/or at least provide a usefulalternative to known composite armour plates.

The reference in this specification to any known matter or any priorpublication is not, and should not be taken to be, an acknowledgment oradmission or suggestion that the known matter or prior art publicationforms part of the common general knowledge in the field to which thisspecification relates.

SUMMARY

In accordance with a first aspect there is provided, an impact absorbingmaterial or armour including an impact absorption layer supported by abacking, the impact absorption layer including a plurality ofsubstantially rigid macroscopic particles arranged in a spacedrelationship relative to one another and a matrix interposed between themacroscopic particles, wherein the matrix is impregnated withsubstantially rigid microscopic particles.

In accordance with a second aspect, there is provided an impactabsorbing material or armour for dissipating energy associated with animpacting projectile, the armour including an impact absorption layersupported by a backing, the impact absorption layer including aplurality of macroscopic particles and a plurality of microscopicparticles which are substantially encapsulated by an at least partiallyflexible matrix, the microscopic particles and macroscopic particlesbeing arranged to interact with one another such that when at least oneof the macroscopic particles is moved during an impact, the movement isat least partially transferred to the microscopic particles therebyassisting to dissipate the impact energy.

In an aspect, the microscopic particles are spherical.

In an aspect, the microscopic particles have a diameter in the range of5 nm to 1 mm.

In an aspect, the microscopic particles are formed from a ceramicmaterial.

In an aspect, the ceramic materials include at least one of glass,silicon, fumed silica, alumina and kaolin clay.

In an aspect, the matrix is composed of between about 10% and 100%microscopic particles.

In an aspect, the matrix includes a polymer material impregnated withthe microscopic particles.

In an aspect, the polymer material is at least one of a flexible orsemi-flexible polymer adapted to retain the macroscopic particles andthe microscopic particles.

In an aspect, the polymer material is at least one of flexible epoxyresin, polyethylene, polypropylene and silicon rubber.

In an aspect, the macroscopic particles are spherical.

In an aspect, the diameter of the macroscopic particles is between about1 mm and 100 mm.

In an aspect, the spacing between the macroscopic particles is betweenabout 0.5 mm and 20 mm.

In an aspect, multiple layers of macroscopic particles are provided,each layer being spaced apart from one another and being substantiallyencapsulated by the matrix.

In an aspect, the size of the macroscopic particles in each layer issubstantially similar.

In an aspect, the sizes of the macroscopic particles in adjacent layersare of a different size.

In an aspect, an outermost layer of the macroscopic particles ispartially exposed from the matrix.

In an aspect, the backing includes side walls thereby bounding theimpact absorption layer.

In an aspect, the backing is formed from at least one of a highlyresilient material and a semi-flexible polymer.

In an aspect, the backing is formed as a composite panel including apolymer material sandwiched between substantially rigid or semi-flexiblesheets.

In an aspect, the plurality of macroscopic particles are arranged in aregular grid and held substantially in place by the matrix.

In accordance with a third aspect there is provided, a material, astructure, a vehicle or clothing including an impact absorbing materialor armour as defined above.

BRIEF DESCRIPTION OF THE FIGURES

The invention is described, by way of non-limiting example only, byreference to the accompanying figures, in which;

FIG. 1 is a side cross sectional view illustrating an example of anarmour material or armour system including an impact absorption layersupported by a backing, in this example, the impact absorption layerincludes two layers of macroscopic particles retained within a matrix;

FIG. 2 is a top view illustrating the example of the armour shown inFIG. 1, the hatched macroscopic particles being the outer or frontlayer;

FIG. 3 a is a perspective view illustrating an example form of a backingof the armour;

FIG. 3 b is a side view illustrating the backing of FIG. 3 a in apartially deformed state;

FIG. 4 is a side cross sectional view of the armour system showing animpacting projectile, the arrows indicating the expected energy transferpatterns of macroscopic particles within an impact absorption layer ofthe armour system;

FIG. 5 is a top view of the armour system shown in FIG. 4, the arrowsindicating energy transfer patterns of macroscopic particles within animpact absorption layer of the armour;

FIG. 6 is a partial side view of two interacting macroscopic particlesand showing the microscopic particles of the matrix between themacroscopic particles, the lines which join the microscopic particlesare shown to represent the interaction of the microspheres asinstantaneous force chains;

FIG. 7 a illustrates a model illustrating the interaction of twomacroscopic particles and the microscopic particles of the matrixbetween the macroscopic particles;

FIG. 7 b illustrates a further model illustrating the interaction shownin FIG. 7 a, with plates (representing the macroscopic particles and/orbacking) and linkages between the plates (representing the microscopicparticles and polymer of the matrix), the linkages being shown asindividual lever segments joined by flexible elbows to represent theinstantaneous force chain interactions;

FIG. 8 a illustrates a simplified model used in example System 1;

FIG. 8 b illustrates a simplified model used in example System 2;

FIG. 9 provides a table including material properties of the NSL-8material;

FIG. 10 a provides a graph of the resultant force on the backing plateof System 1 as shown in FIG. 8 a; and

FIG. 10 b provides a graph of the resultant force on the backing plateof System 2 as shown in FIG. 8 b.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, there is shown an impact or energy absorbingmaterial or armour system 10, referred to hereafter as “armour”, forprotecting an underlying object from a ballistic projectile.

The armour 10 including an impact absorption layer 12 supported by abacking 14. The backing 14 includes bounding walls or sides 15 so as toform a recess 17 in which the impact absorption layer 12 is located andsubstantially housed. The bounding walls 15 contain and protect theimpact absorption layer 12. The impact absorption layer 12 is arrangedto face the direction of a potential incoming projectile and the backing14 is generally located toward, abutted against or incorporated withinan object to be protected such as a person, a vehicle or the like.

The impact absorption layer 12 includes a plurality of substantiallyrigid macroscopic particles 16 arranged in a spaced relationshiprelative to one another and a matrix material 18 interposed between themacroscopic particles 16. The matrix material 18 is impregnated withsubstantially rigid microscopic particles 20 such that the microscopicparticles 20 are distributed throughout the matrix material 18 and arelocated between and around the macroscopic particles 16.

In this example, the macroscopic particles 16 are shown as beingregularly-shaped, more specifically, spherical in shape. The diameter ofthe macroscopic particles 16 may be in the range of about 1 mm to 100mm, and in some examples, in the range of about 4 mm to 20 mm The sizeof the macroscopic particles 16 will be dictated by the physical size ofthe incoming projectiles likely to be encountered by the armour 10. Forexample, larger projectiles will dictate larger macroscopic particles 16to aid in energy absorption.

The macroscopic particles 16 will be constructed of a hard, impactresistant material which typically would be a ceramic such as siliconnitride. The macroscopic particles 16 may be spherical ceramic ballbearings.

The macroscopic particles 16 may be provided in layers in which eachlayer has a plurality of the macroscopic particles 16 in a generallyplanar alignment with one another and the backing 14. Typically, therewould be more than one layer of macroscopic particles 16 to facilitateabsorption and redirection of impact energy. However, a single layer mayalso be used in the simplest example of the armour 10.

In this example, two layers are shown, a first or outer layer 22 ofmacroscopic particles 16 and a second or inner layer 24 of macroscopicparticles 16. However, the armour 10 may include any number of layers,for example, another example of the armour system may include 5 layers.

The macroscopic particles 16 are also positioned and sized in such a wayas to minimise the likelihood of a projectile directly encountering thebacking plate 14 or matrix 18 without coming into contact with themacroscopic particles 16.

Accordingly, each layer of macroscopic particles 16 may be geometricallyoffset or staggered relative one another. This provides an increasedplan form surface area covered by the macroscopic particles 16 as may bebest appreciated from FIG. 2.

Each of the macroscopic particles 16 in the outer layer 22 are spacedapart by distance “A” from the neighbouring macroscopic particles 16.Likewise, each of the macroscopic particles 16 in the inner layer 24 arespaced apart by distance “B” from the neighbouring macroscopic particles16.

The macroscopic particles 16 in each of the outer layer 22 and the innerlayer 24 are also spaced apart by distance “C”. In this example, thedistances “A, B, C” are shown to be the same. However, each of thesedistances may be varied. The distances “A, B, C” may each be in therange of about 0.5 mm to 20 mm, and in some examples, in the range ofabout 0.5 mm to 2 mm Accordingly, each of the layers 22, 24 includesmacroscopic particles 16 arrange in a predetermined and regulararrangement or grid defined by the distances “A, B, C”.

The macroscopic particles 16 in each individual layer may be of similarsize. However, adjacent layers may include macroscopic particles 16 ofdiffering sizes. For example, the inner layer 24 may include macroscopicparticles 16 having a diameter of 8 mm and the outer layer 22 mayinclude macroscopic particles 16 having a diameter of 4 mm.

In this example, the outer layer 22 of macroscopic particles 16 may bepartially exposed to aid in physical deformation of a softer incomingprojectile. In another example of this material system, the outer layer22 of macroscopic particles 16 may also be covered by a cover orbounding plate (not shown) to prevent damage or loss of the outer layer22 of macroscopic particles 16 due to disintegration under repeatedimpact. The bounding plate may be made of a lightweight plastic or ametallic sheet. A material that may be employed in the bounding platemay be a polycarbonate plastic.

In this example, the matrix 18 includes a polymer material 26 and themicroscopic particles 20 are impregnated within and distributed withinthe polymer material 26 of the matrix 18. The polymer 26 may be flexibleor semi-flexible polymer or a similar material with elastomeric bindingproperties.

The polymer 26 may be a tough polymer having a Young's modulus which canvary from 0.001 GPa to 2 GPa. In some examples, the polymer material 26may include or be entirely composed of at least one of flexible epoxyresin, polyethylene, polypropylene or silicon rubber. In some examples,the polymer may be rubberised material.

The macroscopic particles 16 are set within the matrix 18 such that thematrix fills all of the gaps between and substantially encapsulates themacroscopic particles 16. Accordingly, each of the layers 22, 24 arespaced apart from one another and are substantially encapsulated by thematrix 18. The matrix 18 may also be utilised to bond the macroscopicparticles 16 to the backing 14.

In some examples, each of the layers 22, 24 may be formed independentlyas single-macrosphere layers or sheets which can then be glued together(while maintaining the correct orientation of macrospheres 16 from layerto layer). The layer of macrospheres may be held in place by structureswithin a flat mold (not shown) and the matrix 18, (which may be providedin the form of an NSL-8 material as described below with reference toFIG. 9) may be poured or injected into the mold forming one layer whencured. To obtain a multi-layer grid or regular grid of macrospheres,individual sheets may be glued together, for example, using the NSL-8material.

Alternatively, two or more layers of macrospheres can be held in thecorrect grid arrangement by a mold (not shown) and the matrix 18, whichmay in some examples be the NSL-8 material, may be injected into themold under pressure forming one continuous, multi-layer sheet. Thesesheets of macrospheres may then be glued on to the backing plate 14.

The matrix 18 includes a high volume of the microscopic particles 20. Insome example, the volume of the matrix 18 occupied by the microscopicparticles 20 may vary from about 10% to 100%, and in other examples, thevolume occupied by the microscopic particles 20 may vary from 10% to60%. The size of the microscopic particles 20 may vary from 5 nm to 1 mmmicroscopic particles 20 may be regularly shaped particles, morespecifically, spheres such as glass or silicon microspheres ornanospheres. The microscopic particles 20 may take the form of otherregularly shaped objects such as microscopic plates, for example, kaolinclay platelets.

In addition, other regularly shaped objects may be introduced into thematrix 18 to increase its physical integrity and aid in energydissipation. These objects may take the form of short fibres. An exampleof the armour 10 may also contain short aramid, carbon or glass fibreswithin the matrix 18.

The backing 14 is the final component of the armour 10 to encounterincoming impact energy or force. The backing 14 is constructed ofmaterials which provide a high degree of resistance to impact. Thematerial employed in the backing 14 must be capable of momentarydeformation and recovery under impact.

Accordingly, the backing 14 may be in the form of a backing plateconstructed of a material with high toughness and resistance to impactdamage. The backing 14 may be constructed of high-density plastic suchas polycarbonate plastic, steel, aluminium or titanium. The backing 14may be constructed of a single, uniform plate of material such as acomposite plate of fibre cloth set in a rigid or flexible binder or maytake the form of a composite sandwich of plastic or metal plates andsheets of fibre cloth set in a polymer binder as is further detailed inFIGS. 3 a and 3 b.

Referring to FIGS. 3 a and 3 b, the backing 14 may also be constructedas a composite sandwich including one or more layers of microscopictubes 32 (otherwise know as microtubes or nanotubes) sandwiched betweenthe sheets or plates 30 and 31. The microscopic tubes 32 may beair-filled or filled with a fluid.

The plates 30, 31 may be formed from plastic such as polycarbonatesheets or metal and the small tubes 32 are set between the plates 30, 31under pressure. These tubes 32 may take the form of glass-fibre tubes orcarbon nanotubes set in a binding adhesive between the plates 30, 31. Asan alternative to the tubes 32, the backing 14 may incorporate aramidfibre sheets set in a binding adhesive between the plates 30, 31.

Referring more specifically to FIG. 3 b, arrow “D” illustrates themomentary deformation of the surface plate 30 which may occur when aprojectile impacts the armour 10. The deformation of the surface plate30 is communicated to the tubes 32 which in turn deform in response tothe movement of the surface plate 30.

In this example, the deformation of the surface plate 30 is not directlyexperienced by the lower plate 31 or other parts of the backing 14 whichcan be a source of backing plate critical failure. The deformation ofthe hollow tubes 32 causes compression and movement of air or fluidwithin the tubes 32 which consumes a percentage of the incoming energyassociated with the impacting projectile. The tubes 32 also experience arecovery force due to their elastic nature and this is communicated tothe front plate 30 which assists the shape recovery of the front plate30.

In yet another example form, the backing 14 may be constructed of asemi-flexible elastomeric material or as a segmented or reticulatedarrangement of rigid metal or plastic plates. The flexible backing incombination with the flexible impact absorption layer 12 provides aflexible example of the armour 10.

Turning now to the function of the above described impact absorbingarmour material or armour system 10, it may be appreciated that thearmour 10 includes a combination of rigid and flexible components thatwork together as a system to absorb, dissipate or redirect the energyassociated with an incoming ballistic projectile.

Referring to FIGS. 4 and 5, the armour 10 is shown with an impactingprojectile 40 normal to the armour 10 surface. The arrows “E” shown inthe Figures provide indicative representations of the pathways of energyand force dissipation likely to be encountered during impact of theprojectile.

During such an impact, the macroscopic particles 16 are initiallyimpacted by the projectile 40 and undergo constrained movement withinthe flexible or semi-flexible matrix 18. The backing 14 supports andcontains the macroscopic particles 16 and the flexible matrix 18. Thebacking 14 provides a final impacting structure to stop the projectile40.

Accordingly, it may be appreciated that the armour 10 provides threemain components which function together as a system for absorbing,dissipating or redirecting the energy associated with the incomingballistic projectile 40. The three main components are: the macroscopicparticles 16, the flexible or semi-flexible matrix 18 and the backing14.

Turning firstly to the function of the macroscopic particles 16, thehardness of the macroscopic particles 16 act to deform the relativelysoft metallic projectile due to the velocity and kinetic energy of theimpact. This primary deformation of the projectile increases its surfacearea thus decreases its penetrative potential. Due to the increasedsurface area of the deformed projectile, the likelihood of itencountering and interacting with more macroscopic particles 16 isincreased.

As the projectile encounters an increasing number of macroscopicparticles 16, the mass of the impact system increases, therebydecreasing the velocity and hence the kinetic energy of the projectile40.

During such an impact there is also interaction between the adjacentmacroscopic particles 16 and between macroscopic particles 16 and thebacking 14. As a projectile strikes the energy absorption layer 12, theprojectile 40 makes physical contact with one or more macroscopicparticles 16. These macroscopic particles 16 react to the impact withconstrained motion within the matrix 18. The energy of the impact isthus spread laterally throughout the energy absorption layer 12 as wellas towards the backing 14 as more and more macroscopic particles 16 movein response to the impact.

Due to the arrangement of the layers of the macroscopic particles 16,the macroscopic particles 16 directed toward the backing 14 arepredominantly at an angle to the backing surface less than 90 degrees.It is also noted that due to the physical properties chosen for thebacking 14, impact at less than 90 degrees is far more likely to cause adeflection of the incoming energy or force thus minimising thelikelihood of penetration.

Turning now to the second main component of the armour 10, the matrix18. There are two mechanisms of energy dissipation within the matrix 18.

The first mechanism of the matrix 18 relates to the conservation ofmomentum whereby an impulse of energy caused by an impact event has theeffect of producing a shock-wave that travels through a medium andcauses damage to that medium. As the shock wave travels through thematrix 18, the shock wave encounters more and more microscopic particles20 which are located within the matrix 18.

The microscopic particles 20 are forced into constrained motion withinthe polymer material 26 of the matrix 18. This motion of the microscopicparticles 20 incorporates their mass, momentum and inertia into thesystem of impact. This has the effect of dampening the motion andabsorbing the energy of the shock wave in motion and heat.

The second mechanism of the matrix 18, relates to the inertia linkagefor the microscopic particles 20 as is shown in FIG. 6 also referred toas instantaneous force chains. In this Figure, the left hand macroscopicparticle 16 undergoes an initial impulse in direction “F” of the righthand macroscopic particle 16.

The matrix 18, more specifically, the microscopic particles 20 locatedwithin the polymer material 26, provide elastic linkages or “pathways”also referred to as instantaneous force chains, shown as “H” to transferenergy between the microscopic particles 20 and ultimately themacroscopic particles 16. The matrix 18 absorbs at least a portion ofthe energy associated with the initial impulse such that the right handmacroscopic particle 16 undergoes a reduced impulse relative to the lefthand macroscopic particle 16 in direction “G”.

Accordingly, the energy dissipation in the matrix 18 includes:instantaneous force chain interactions between adjacent microscopicparticles 20; redistribution of vectors into a random cloud or mass ofthe microscopic particles 20; and the mass of the microscopic particles20 which undergo constrained movement to dissipate energy via heat.

Referring to FIG. 7 a, due to the inertia of the microscopic particles20 within the matrix 18, a rapid impulse of energy is less likely tocause them to slide past one another. A rapidly applied force will takethe path of least resistance which is directly through instantaneousforce chains between which can spread out in all directions from thepoint of impulse.

These instantaneous force chains, indicated with the letter “J” in FIG.7 a, dissipate the energy or force throughout the matrix 18 allowing thematrix 18 to encounter a greater area or amount of the macroscopicparticles 16, the backing 14 and the bounding sides 15 of the backing14.

Referring to 7 b, an analogy may be drawn wherein the matrix 18, inparticular the interaction of the microscopic particles 20 within thepolymer 26, are considered to behave as a multitude of small,interconnected inflexible levers 50 linked by flexible elbows 52. Thelevers 50 and elbows 52 providing an analogous linkage between impactreceiving structures which in this example include plates 54, 56 and 58.

If the impulse is a rapid short event and the levers 50 inhibit theelbows 52 from rotating, more of the impulse is transferred from plate54 to plates 56 and 58. However, if the impulse is a slower, longerduration event, the inertia of the levers 50 can be overcome and thelevers 50 will merely rotate about the elbows 52 which results in verylittle of the impulse being transferred from the plate 54 to plates 56and 58.

As may be appreciated from the FIG. 7 b, the initial impulse is spreadover a larger surface area. In this example, two plates 56, 58 areaffected by the impulse received by the first plate 54 which dissipatesand propagates the force to a larger area.

The third major component for energy dissipation is provided by thebacking 14. The backing 14, in particular the materials and constructionselected for the backing 14 as has been described above, are adapted tomomentarily deform under stress and recover without critical failure.

The backing 14 represents a large surface for final energy dissipation.This large surface area is made accessible for energy dissipation by theinteraction of the macroscopic particles 16 and the microscopicparticles 20 set within the matrix 18.

Comparative Analysis Example

Referring now to FIGS. 8 a, 8 b, 9, 10 a and 10 b along with Equation 1below, there is provided a simplified comparative mathematicallymodelled example to compare the performance of two armour systems orarrangements, System 1 and System 2.

The first armour system, System 1 as shown in FIG. 8 a, is a simplifiedexample of the reactive armour system 10 as substantially hereinbeforedescribed and like numerals are used to denote like parts. Accordingly,System 1 includes three major elements being: the macrospheres 16 a, 16b and 16 c held in a regular grid but not in direct contact with eachother or the backing plate; a flexible rubberised matrix 18 containingmicrospheres 20 and also holding the macropsheres 16 a, 16 b and 16 c ina regular grid; and a backing plate 14.

In System 1, the diameter, D₁, of the macrospheres 16 a, 16 b and 16 cis 10 mm, the distance, D₂, between the macrospheres is 1mm and thedistance, D₃, between the outer edge of the macrospheres 16 b, 16 c andan edge of the model is 5 mm and the overall width, D₄, is 31 mm. Thedistance, D₅, is about 9.5 mm and the distance D6 is 6 mm.

System 2, is shown in FIG. 8 b, and comprises only hard macrospheres 16a, 16 b and 16 c held in a regular grid in direct contact with eachother and with the backing plate 20. Accordingly, the primary differencebetween System 1 and System 2, is that System 1 includes spacing betweenthe macrospheres and the backing 14, and the matrix 18 includingmicrospheres 20 held by a rubberised material.

In System 2, the diameter, D₁, of the macrospheres 16 a, 16 b and 16 cis 10 mm, and the macrospheres 16 b and 16 c are arranged to directlyabut the backing plate 14. The angle, A₁, is 40 degrees and as such theangle between the points of contact with the backing plate 14 and impactforce, F₀, is 20 degrees.

Referring to FIG. 9, there is shown material data for NSL-8 which is aflexible epoxy material having microparticles that may be used as abinder material. The NSL-8 material was developed by and may be obtainedfrom Thermal Mitigation Technologies of Louisiana, USA. In the example,the NSL-8 material is used to approximate the behaviour of the matrixmaterial 18 in System 1. The NSL-8 material is used in this example dueto the availability of the material data. However, matrix materials 18other than the NSL-8 material may also be utilised.

General Experimental Model Approximations

Turning now to the models used to approximate and compare the backingplate impact forces (as shown in FIGS. 10 a and 10 b) of System 1 andSystem 2, a number of approximations were made in order to simplify themodels and calculations. These approximations were as follows:

-   -   1. The armour systems were modelled only two dimensionally as a        cross-section. In a three-dimensional model, force will be more        effectively distributed since more macrospheres will become        involved in the interaction but since this is a comparative        simulation and the phenomenon will be observed in both models,        this can be ignored;    -   2. In order to standardise and simplify the comparison, only 3        macrospheres and their interactions with each other and the        backing plate were considered in both models. The macrospheres        were arranged in a triangular “billiard ball” pattern with one        macrosphere on the surface of the armour plate and two        macrospheres behind it near to the backing plate;    -   3. The impulse will only be considered in an optimal position        normal to the surface of the armour plate and on the central        axis of the lead macrosphere. In addition, only force components        normal to the backing plate will be considered in the final        comparison;    -   4. A destructive impact will not be considered for the purposes        of this comparison since all that is of interest in this        instance is a comparison of how well each armour system        distributes forces into the backing plate;    -   5. The sizes of the macrospheres in both models will be        standardised to 10 mm diameter for the purposes of this        comparative simulation;    -   6. In System 1, only the first impulse will be analysed and not        the subsequent oscillations of the macrospheres and the        microspheres which will in turn produce further force        reverberations through the matrix. The reflections off the        backing plate will not be considered either since all subsequent        impulse forces will be smaller in magnitude than the primary        impulse due to frictional energy loss;    -   7. In order to further simplify the comparative model,        frictional forces and associated losses will not be taken into        account;    -   8. It is assumed in this model that the hard macrospheres and        backing plate are incompressible.

Model Development

Taking into account the above approximations, the experimental model forSystem 1 was developed around the approximation of the matrix material(being a flexible epoxy or rubberised material impregnated withmicrospheres) behaving similarly to a granular material when impacted.This approximation has been used because granular materials approach thebehaviour of a rubberised solid due to interactions between theindividual particles often referred to as instantaneous force chains (asfor example shown in FIGS. 7 a and 7 b). The approximation of the matrixmaterial being modelled as a granular material may be considered aconservative approximation for the behaviour the actual matrix materialas the flexible polymer, being a rubber like or rubberised material, mayabsorb further impact energy in comparison to a purely granularmaterial.

In particular, the assumption of a loose granular material has beenapplied whereby the interactions between the elements, in this instancethe macrospheres 16 a, 16 b and 16 c, are modelled as instantaneousforce chains or linkages between the elements. The instantaneous forcechains or linkages are provided with material properties, in thisexample for the NSL-8 material, such as a Young's Modulus so as to aleast partially account the energy transfer and distribution of such amaterial between the macrospheres 16 a, 16 b and 16 c.

Accordingly, System 1 may be modelled in accordance with the followingequation:

$\begin{matrix}{{{Force}\mspace{14mu} {Model}\mspace{14mu} {for}\mspace{14mu} {System}\mspace{14mu} 1}{\partial_{zz}{= {\frac{F_{0}}{2\pi}\frac{2\left( {\partial_{1}{+ \partial_{2}}} \right){z^{2}\left\lbrack {{{\partial_{1}{\partial_{2}x}}\mspace{11mu} \cos \; \theta_{0}} + {x\; \sin \; \theta_{0}}} \right\rbrack}}{\left\lbrack {\left( {\partial_{1}z^{2}} \right) + x^{2}} \right\rbrack \left\lbrack {\left( {\partial_{2}z^{2}} \right) + x^{2}} \right\rbrack}}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In the model the following variables are utilised:

${\partial_{1}{= {r + \frac{\sqrt{\left( {r^{2} - t} \right)}}{t}}}};$${\partial_{2}{= {r + \frac{\sqrt{\left( {r^{2} - t} \right)}}{t}}}};$${t = \frac{E_{x}}{E_{z}}};$$r = {0.5\; {E_{x}\left( {\frac{2}{G} - \frac{V_{z}}{E_{z}} - \frac{V_{x}}{E_{x}}} \right)}}$

It is noted that due to the response of a granular material, Equation 1utilises t<r² and r>0. The material and physical data propertiesutilised are as follows:

-   -   E_(x)=0.0344 (Young's Modulus in GPA in X axis);    -   E_(z)=0.0344 (Young's Modulus in GPA in Z axis);    -   V_(x)=0.5 (Poisson ratio in X axis);    -   V_(z)=0.5 (Poisson Ratio in Z axis);

${G = {\frac{E_{x}}{2\left( {1 + V_{x}} \right)}\mspace{14mu} \left( {{Shear}\mspace{14mu} {Modulus}} \right)}};$

-   -   θ=0.0 (Angle of F₀ to the Z-axis which in this case is zero as        the impacting force is aligned with the Z-axis);    -   F₀=1 (impact force of 1 Newton).

The experimental model example for System 2, is derived from a simplevector diagram. Since the macrospheres (16 a, 16 b and 16 c) are indirect contact with each other and the backing plate, at the instant offorce application, force will be communicated directly through themacrospheres into the backing plate. There are no intervening mechanismswhich might further dissipate this force. Due to the two path-wayspresented by the macrosphere arrangement chosen for the model of System2, the force is effectively split in two (aside from the smallcomponents that are lost due to being at right angles to the axis of thebacking plate).

$\begin{matrix}{{{Force}\mspace{14mu} {Model}\mspace{14mu} {for}\mspace{14mu} {System}\mspace{14mu} 2.}{{F_{2} = {\frac{F_{o}}{2}{\cos (\theta)}}};}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

In the model the following variables are utilised:

-   -   θ=20° (Angle between Z-axis and contact point with backing        plate, as shown in FIG. 8 b).    -   F₀=1 (impact force of 1 Newton).

This force is expressed at the points where each of the back twomacrospheres make contact with the backing plate, causing two forcespikes, as is shown and further described in relation to FIG. 10 bbelow.

System 1—Description of the Model for Force Impact:

Referring again to FIG. 8 a, the impulse force will first be encounteredby the primary sphere, 16 a. Under this impulse force, it will generatea force distribution within the matrix 18 which is felt in part by thetwo back macrospheres 16 b, 16 c and a proportion of which is felt bythe backing plate 14. The two back macrospheres 16 b, 16 c will in turngenerate their own force distributions within the matrix 18 due to theforce exerted on them by the first macrosphere 16 a. These secondaryforce distributions will be felt along with the remnant of the firstmacrosphere force distribution by the backing plate 14.

There are two dominant methods of force dispersal through the matrix 18which will be taken into account in this simulation. 1. Through forcepropagation through the flexible matrix 18 via instantaneous force chaininteractions between microspheres 20 in direct contact or close enoughto form instantaneous force chains. 2. Through interactions within thematrix 18 between the macrospheres 16 a, 16 b and 16 c

The first macrosphere 16 a will react with constrained movement withinthe flexible matrix 18 due to the unity force acting on it. i.e. It willexperience an acceleration due to the impulse force (F) but will alsoexperience a deceleration due to the resistance of the flexible matrix18. The first macrosphere 16 a will produce forces similar in magnitudeand direction to the forces produced by a static force pressing down ona flexible half-solid by a submerged, inflexible sphere.

The force acting on the plane which fully intersects the two remainingmacrospheres 16 b, 16 c will be calculated. The resultant force actingon the remaining two macrospheres 16 b, 16 c will become the sum of theforces contained in the plane cut that intersect the macrospheres 16 b,16 c.

The remaining two macrospheres 16 b, 16 c will be stimulated intomovement in the same way as the first macrosphere 16 a and will in turnproduce their own force distribution pattern in the matrix. The forcefelt by the two back macrospheres 16 b, 16 c will be subtracted from theprimary force exerted by the first macrosphere 16 a. Finally theresultant force distribution felt by the backing plate 14 will be thesum of the forces exerted by all the macrospheres 16 a, 16 b, 16 c. Thisresultant force distribution is plotted in FIG. 10 a.

System 2 Description:

Referring again to FIG. 8 b, System 2 is comprised of rigid spheres 16a, 16 b, 16 c in contact with each other and with the backing plate 14.Accordingly, compression of the macrospheres 16 a, 16 b, 16 c and thebacking plate 20 is not considered in this model and the forcedistribution becomes quite simple. The incoming unity force iscommunicated instantaneously to the backing plate via the contact pointsbetween the macrospheres and the backing plate. The force vectors normalto the backing plate may appear in two locations at the contact pointsbetween the back two macrospheres and the backing plate. These two force“spikes” are plotted on a graph for comparison with the resultant forcedistribution graph produced for System 1. This resultant forcedistribution is plotted in FIG. 10 b.

Referring now more specifically to FIG. 10 a, the results demonstratethat System 1 produces a more continuous spread of force over the lengthof the backing plate with two peaks at the points closest to the backtwo macrospheres. The magnitude of the force spikes for System 1, inthis example, is 0.11 N.

In comparison, and now referring additionally to FIG. 10 b, it isdemonstrated that System 2 produces two discrete, discontinuous forcespikes at the points of contact between the macrospheres and the backingplate. In this example, the magnitude of the force spikes for System 2is 0.45 N which is over 4 times the force produced by System 1.

Accordingly, System 1 is better able to distribute the impact force andreduce the point force load on the backing plate and as such System 1,which is representative, of the armour 10 according to the inventiondescribed herein may provide advantageous impact absorbing properties,shielding and protection in comparison to previously known systems,which may function in a similar manner to that modelled above inrelation to System 2.

In the light of the above, it may be appreciated that the abovedescribed impact absorbing material provided in the form of an armourplate system provides a rigid or semi-rigid plate of any shape and sizewhich can be deployed to protect personnel, property or vehicles whichare subject to projectile attack.

The armour material or armour plate system may take a number of physicalconfigurations and may be deployed or arranged as an armour plates orother structure having continuous, unbroken armoured surface or as aseries of discrete, interlocked or segmented pieces forming asemi-flexible whole (scale armour). When formed as scale armour, thearmour system may be utilised as or for producing personal body armourfor use by military or law-enforcement personnel. The armour platesystem described herein may be formed as a stand alone armour plate orpanel, or incorporated within another structure such as a side wall of avehicle or clothing.

Advantageously, the material and armour system described herein includesa number of interacting components or sub-systems which interact withone another to deflect, dissipate and absorb energy associated with animpacting projectile such as a bullet. As described above, thesecomponents or sub-systems include the macroscopic particles, the matrixwhich includes the polymer impregnated with the microscopic particlesand the backing.

More specifically, when the armour system or plate is impacted the hardmacroscopic particles undergo constrained motion within the matrix.During this constrained motion the microscopic particles set within thepolymer of the matrix also undergo constrained motion and dissipate theimpact throughout the energy absorption layer and the backing. Thebacking also interacts with the matrix and hence the macroscopicparticles so as to absorb energy from and physically restrain or containthe energy absorption layer.

While specific examples of the invention have been described, it will beunderstood that the invention extends to alternative combinations of thefeatures disclosed or evident from the disclosure provided herein.

Many and various modifications will be apparent to those skilled in theart without departing from the scope of the invention disclosed orevident from the disclosure provided herein.

1. (canceled)
 2. Armour for dissipating energy associated with animpacting projectile, the armour including an impact absorption layersupported by a backing, the impact absorption layer including: aplurality of macroscopic particles arranged in a spaced relationshiprelative to one another; and an at least partially flexible matrixinterposed between the plurality of macroscopic particles; wherein thematrix is impregnated with substantially rigid microscopic particles soas to flexibly locate the microscopic particles between the macroscopicparticles such that movement of at least one of the macroscopicparticles by the impacting projectile is at least partially transferredto an adjacent at least one of the macroscopic particles by themicroscopic particles thereby assisting to dissipate the impact energy.3. The armour according to claim 2, wherein the microscopic particlesare spherical.
 4. The armour according to claim 2, wherein themicroscopic particles have a diameter in the range of about 5 nm to 1mm.
 5. The armour according to claim 2, wherein the microscopicparticles are formed from a ceramic material.
 6. The armour according toclaim 5, wherein the ceramic materials include at least one of glass,silicon, fumed silica, alumina and kaolin clay.
 7. The armour accordingto claim 2, wherein the matrix is composed of between about 10% and 100%microscopic particles.
 8. The armour according to claim 2, wherein thematrix includes a polymer material impregnated with the microscopicparticles.
 9. The armour according to claim 8, wherein the polymermaterial is at least one of a flexible or semi-flexible polymer adaptedto retain the macroscopic particles and the microscopic particles. 10.The armour according to claim 9, wherein the polymer material is atleast one of flexible epoxy resin, polyethylene, polypropylene andsilicon rubber.
 11. The armour according claim 2, wherein themacroscopic particles are spherical.
 12. The armour according to claim11, wherein the diameter of the macroscopic particles is between about 1mm and 100 mm.
 13. The armour according to claim 11, wherein the spacingbetween the macroscopic particles in the between about 0.5 mm and 20 mm.14. The armour according to claim 2, wherein multiple layers ofmacroscopic particles are provided, each layer being spaced apart fromone another and being substantially encapsulated by the matrix.
 15. Thearmour according to claim 14, wherein the size of the macroscopicparticles in each layer is substantially similar.
 16. The armouraccording to claim 14, wherein the sizes of the macroscopic particles inadjacent layers are of a different size.
 17. The armour according toclaim 2, wherein an outermost layer of the macroscopic particles ispartially exposed from the matrix.
 18. The armour according to claim 2,wherein the backing includes side walls thereby bounding the impactabsorption layer.
 19. The armour according to claim 2, wherein thebacking is formed from at least one of a metal such as titanium oraluminium, a composite plate of fibre cloth set in a rigid or flexiblebinder or a highly resistant material and a semi-flexible polymer. 20.The armour according to claim 2, wherein the backing is formed as acomposite panel including a polymer material sandwiched betweensubstantially rigid or semi-flexible sheets.
 21. The armour according toclaim 2, wherein the plurality of macroscopic particles are arranged ina regular grid and held substantially in place by the matrix. 22.(canceled)